1. Field of the Invention
The invention concerns apparatus for the separation of two kinds of granular solid particles of any shape and of different density that have been graded to an upper limit of their grain size.
2. Description of the Prior Art
Many devices and apparatuses are already known for the separation of mixtures of solid particles of different density by means of flow media, e.g. for panning, elutriation, air sifting etc. A known and simple apparatus consists of a tubular counterflow separator column wherein the mixture fed in through an inlet aperture is exposed to the effect of a flow medium flowing through the tube from the bottom towards the top. The particles of lighter material are carried upwards by the flow medium and are discharged from the separating column together with the flow medium, through an upper outlet aperture while the particles of heavier material sink down in the flow medium and are collected in a collecting vessel at the bottom of the pipe.
It is common to all known separating apparatus that good separation results can only be achieved with mixtures of relatively uniform grain size and grain shape. Accordingly, therefore, the mixture of the raw material has to be pre-treated e.g. by grinding, grading, sifting etc. Such pretreatment renders the in itself simple separation of a mixture in a counterflow separator column elaborate and in most cases a multi-stage separating process is necessary to obtain satisfactory results.